ASEP_ NSCP 2015 Chapter6 - WOOD.pdf

Chapter 6

NATI ONAL STRUCTU NATI S TRUCTU RA RAL L CODE CO DE OF THE PH ILI PP PPIN IN ES VOLUM VOL UM E 1 BUI LDIN GS, TOWER TOWERS S AND O TH ER VERTI VERTI CA CAL L STRUCTU RE RES S SEVENT SE VENT H EDIT EDIT ION, 2015

Ariel P. Santos, F.ASEP Co-Chairman, Wood Committee

WOOD substance that that trees trees are are made made  the substance out of. fibrous structural structural tissue  the hard, fibrous that is commonly found in the stems and roots of the trees.  the material we obtain from trees.

TRIVIA: The term “WOOD” occurred 303 times in Chapter 6 of NSCP 2015

WOOD substance that that trees trees are are made made  the substance out of. fibrous structural structural tissue  the hard, fibrous that is commonly found in the stems and roots of the trees.  the material we obtain from trees.

TRIVIA: The term “WOOD” occurred 303 times in Chapter 6 of NSCP 2015

TIMBER

TIMBER TRIVIA: The term “TIMBER” occurred 110 times in Chapter 6 of NSCP 2015

TIMBER is still still attached attached to  the wood that is the ground. its bark bark still still on. on.  the wood with its Timber Timber still still has to to be cut cut and processed for it to be sold for construction purposes. U.S. and Canada, Canada, ‘timber’ ‘timber’ usually usually  in U.S. refers refers to to felled felled trees. trees. 2015, ‘Timber’ ‘Timber’ are square square or  In NSCP 2015, nearly square sawn lumber that is not less less than 125 mm mm wide. wide.

LUMBER

LUMBER TRIVIA: The term “LUMBER” occurred 139 times in Chapter 6 of NSCP 2015

LUMBER  rough lumber is the raw material, which can be processed and then used for a variety of functions.  finished lumber is the wood that has already been processed and usually available in various sizes than can be immediately used without requiring much cutting or shaping.  a relatively new term compared to timber

Basic References 

National Structural Code 0f the Philippines 2010 (NSCP 2010) TRIVIA: Many of the provisions and tables date back to the 1 st Edition of the National Structural Code for Buildings (NSCB 1972)



To keep with the times, sections 615 to 619 has been adopted from the National Design Specification for Wood Construction (NDS 2015)

Sections 601 to 604 SECTION 601 - GENERAL REQUIREMENTS SECTION 602 - NOTATIONS AND DEFINITIONS NOTE: NOTATIONS HAS BEEN ADDED SECTION 603 - MINIMUM QUALITY SECTION 604 - DESIGN AND CONSTRUCTION REQUIREMENTS NOTE: Almost the same with NSCP 2010 



With minor corrections to conform with the NSCP 2015 updates Tables were re-arranged so as they appear right after the first time they were mentioned as practically as possible

Sections 605 to 613 PART I - REQUIREMENTS APPLICABLE TO ALL DESIGN PROCEDURES SECTION 605 SECTION 606 SECTION 607 SECTION 608 SECTION 609 SECTION 610 SECTION 611 SECTION 612 SECTION 613

- DECAY AND TERMITE PROTECTION - WOOD SUPPORTING MASONRY OR CONCRETE - WALL FRAMING - FLOOR FRAMING - EXTERIOR WALL COVERINGS - INTERIOR PANELING - SHEATHING - MECHANICALLY-LAMINATED FLOORS AND DECKS - POST–BEAM CONNECTIONS

NOTE: Almost the same with NSCP 2010 With minor corrections to conform with the NSCP 2015 updates Tables were re-arranged so as they appear right after the first time they were mentioned as practically as possible

Sections 614 PART II - REQUIREMENTS APPLICABLE TO DESIGN OF WIND AND EARTHQUAKE LOAD-RESISTING SYSTEMS SECTION 614 - WOOD SHEAR WALLS AND DIAPHRAGMS NOTE: The same with NSCP 2010

Section 615 DESIGN VALUES FOR STRUCTURAL MEMBERS

615.1 General 615.2 Reference Design Values 615.3 Adjustment of Reference Design Value Reference Design Values ( , , , ,

,

)

Adjusted Reference Design Values ( ′, ′, ′, ′ , ′ , ′)


615.2 Reference Design Values 





Table 6.1 Working Stresses for Visually Stress-Graded Unseasoned Structural Timber of Philippine Woods of NSCP 2010 has been renamed as Table 615.2-1 Reference Values for Visually Stress-Graded Unseasoned Structural Timber of Philippine Woods Table for Reference Values for 63% Stress Grade has been restored Table for References Values for additional species of Philippine Woods has been placed immediately after Table 615.2-1


615.3.2 Load Duration Factor, CD Table 615.3-1 Load Duration Factors 1,

Load Duration

Typical Design Loads

Permanent

0.9

Dead Load

Ten years

1.0

Occupancy Live Load

Seven days

1.25

Construction Load

One day

1.33

Earthquake Load

One day

1.33

Wind Load (Connections and Fasteners only)

Ten minutes Impact2

1.60 2.0

Wind Load (members) Impact Load

1

When using the Alternative Basic Load Combinations of Chapter 2, the one-third increase shall not be used concurrently with the Load Duration Factor, .

2

Load duration factor greater than 1.6 shall not apply to structural me mbers pressure -treate d wi th wat er-borne preservatives or fire retardant chemicals. The impact load duration shall not apply to connections.


615.3.3 Temperature Factor, Ct

NEW

Table 615.3-2 Temperature Factor, Reference Design Values

, , and 1

,

In Service Moisture Conditions1

≤

<

≤

°

°<

≤

Wet or Dry

1.0

0.90

0.90

Dry

1.0

0.80

0.70

Wet

1.0

0.70

0.50

Wet service condition for sawn lumber is defined as in service moisture content greater than 19%. Wet service condition for glued laminated timber is defined as in service moisture content of 16% or greater.

Section 616 DESIGN PROVISIONS AND EQUATIONS

616.1 616.2 616.3 616.4 616.5 616.6 616.7 616.8 616.9 616.10

General Bending Members - General Bending Members – Flexure Bending Members – Shear Bending Members - Deflection Compression Members - General Solid Columns Tension Members Combined Bending and Axial Loading Design for Bearing


ERRATA: Section 616.3.3.8 should read like this.

This part is missing but can also be found under Table 617.3-1

Section 616 DESIGN PROVISIONS AND EQUATIONS There has been a mix616.3.3 Beam Stability Factor, CL NOTE: up between the Slenderness

For laterally supported beams, CL = 1.0 616.3.3.8 When lateral support to compression side of beam may permit beam to buckle laterally, the beam stability factor, , shall be calculated as follows: =

where ∗

⁄

+ .

∗

−

Factor Adjustment for Beams (NSCP 2001) and this Beam Stability Factor Adjustment in the Fourth Printing of NSCP 2010 ⁄

+ .

∗

−

⁄

∗

.

= Reference bending design value multiplied by all applicable adjustment factors except , MPa , , and = =

.

where

< 50

This factor CL is compatible with Column Stability Factor, Cp.


Note:

′

= Reference modulus of elasticity value multiplied

NEW

by all applicable adjustment factors = Reference modulus of elasticity for beam and

′, For value of just refer to Table 617.3-1 under Section 617.3.1

column stability = .

.

.

/

.

= Modulus of elasticity level exceeded by about 95% of the individual pieces =

–

.

= Reference modulus of elasticity = coefficient of variation in modulus of elasticity = 0.25 for Visually graded sawn lumber = 0.11 for Machine Stress Rate lumber

.

= adjustment factor to convert bending basis

.

= factor of safety

values to a pure

SAMPLE COMPARISON OF VALUES OF F b

’

N S C P 2 0 1 5 v s . N S CP 2 0 0 1

′ =

18

BASIS OF GRAPH:

16

63% visually stress-graded Guijo Fb = 17.10 MPa Adjustment factors other than CL taken as 1.0 E = 6,670 MPa COVE =0.25

14

NSCP 2001:

12 10 ′

′ =

−

NSCP 2015: 8 6 4

′ =

.

NSCP 2001 NSCP 2015

2 0 0

10

′ =

20

=

30

⁄

+ NSCP 2001

.

40

∗

−

50

⁄

+ NSCP 2015

.

60

∗

−

⁄ .

∗

Section 616 DESIGN PROVISIONS AND EQUATIONS Table 616.3-1 Effective Length, Cantilever 1

, for Bending Members ⁄

where

<

where

⁄

≥

Uniformly distributed load

=

.

=

.

+

Concentrated load at unsupported end

=

.

=

.

+

Single Span Beam1,2

where

⁄

<

where

⁄

≥

Uniformly distributed load

=

.

=

.

+

Concentrated load at center with no intermediate lateral support

=

.

=

.

+

Concentrated load at center with lateral support at center

=

.

Two equal concentrated loads at 1/3 points with lateral support at 1/3 points

=

.

Three equal concentrated loads at 1/4 points with lateral support at 1/4 points

=

.

Four equal concentrated loads at 1/5 points with lateral support at 1/5 points

=

.

Five equal concentrated loads at 1/6 points with lateral support at 1/6 points

=

.

Six equal concentrated loads at 1/7 points with lateral support at 1/7 points

=

.

Seven or more equal concentrated loads, evenly spaced, with lateral support at points of load application

=

.

Equal end moments

=

.

1

2

For single span or cantilever bending members with loading conditions not specified in Table 616.3 -1: ⁄ < = . where ⁄ ≤ = . + where ≤ . ⁄ > where = . . Multiple span applications shall be based on table values or engineering analysis .

Note: This table gives a very clear definition of effective length


616.4 Bending Members - Shear =

Shear Design Equations:

in general;

=

for rectangular section

Note:

≤

′

For beams notched at tension face: for rectangular section :

’=

for circular section

:

’=

for gradual notch

:

’=

Note:

≤

′

d

dn

d

dn

′ ′


616.4 Bending Members - Shear For beams notched at compression face of rect. section: when e ≤ dn :

’=

when e > dn :

’=

− ′

For beams notched at compression face of rect. section: when x < 5d :

’=

Unloaded Edge

d de

when x ≥ 5d :

’=

′ de

d

Note:

≤

d

′ Unloaded Edge

Unloaded Edge

de


616.5 Bending Members - Deflection 616.5.2 Long-Term Loading Total deflection, ∆ =

∆

+ ∆

where = time dependent deformation (creep) factor = 1.5 for seasoned lumber and glulam in dry service condition = 2.0 for glulam in wet service condition = 2.0 for unseasoned lumber or seasoned lumber in wet service cond. ∆

= immediate deflection due to the long-term component of the design load, mm.

∆

= deflection due to the short-term or normal component of the design load, mm.


616.6 Compression Members Column – refers to all types of compression members, including members forming part of trusses or other structural components Simple Solid Wood Columns – consists of a single piece or of pieces properly glued together to form a single member.

Section 616 DESIGN PROVISIONS AND EQUA EQUATIONS TIONS

ERRAT ERRA TA: Section 616.7.1.5 should read like this. all should be replaced with

missing

∗

Section 616 DESIGN PROVISIONS AND EQUA EQUATIONS TIONS

616.7.1 Column Stability Factor, Factor, CP For laterally supported columns, CP = 1.0 For laterally laterally unsupported unsupported columns, columns, when slendern slenderness ess ratio, ratio, =

where

+

⁄

=

∗

+

−

⁄

∗

−

. ⁄

c = 0.80 for sawn lumber c = 0.85 for round timber poles or piles c = 0.90 for structural glulam timber, structural composite lumber, and cross laminated timber

⁄

∗

=

, is < 50,

SAMPLE COMPARISON OF VALUES OF F c

’

N S C P 2 0 1 5 v s . N SC SC P 1 9 9 2

BASIS OF GRAPH:

12

63% visually stress-gr stress-graded aded Guijo Guijo

′=

10

Fc = 10.4 10.40 0 MPa MPa 8

Adjustment factors other than CP taken as 1.0

NSCP 1992:

6

′

′ =

4

−

ℓ ⁄

E = 6,6 6,670 70 MPa COVE =0.25

NSCP 2015:

′ =

2

. ℓ ⁄

NSCP 1992 NSCP 2015

0 0

10

′=

20

=

+

30 NSCP 1992

⁄

∗

40 NSCP 2015

−

+

⁄

50

∗

−

⁄

⁄

60

∗


616.7.2 Tapered Columns Use of

: =

+

−

−

.

−

where = representative dimension for tapered column, mm = the minimum dimension for that face of the column, mm = the minimum dimension for that face of the column, mm

Value of

(depends on column end support conditions): = . when large end is fixed, small end unsupported or simply supported = . when small end is fixed, large end unsupported or simply supported = . when both ends are simply supported, tapered toward one end = . when both ends are simply supported, tapered toward both ends

For all other support conditions: =

+

−


616.7.3 Round Columns The design of a column of round cross section shall be based on the design calculations for a square column of the same crosssectional area and having the same degree of taper. TRIVIA: The column stability factor for rectangular columns can be used for other column shapes by substituting for in computing . =

. ⁄

=

. ⁄


616.8 Tension Members Basic requirement:

≤

′


616.9 Combined Bending and Axial Loading 616.9.1 Bending and Axial Tension +

∗

≤

.

and

∗∗

≤

.

where: ∗

= reference bending design value multiplied by all applicable adjustment factors except , MPa. ∗∗

= reference bending design value multiplied by all applicable adjustment factors except , MPa.

Section 616 DESIGN PROVISIONS AND EQUATIONS 616.9.1 Bending and Axial Compression +

+

≤

.

and +

where: and and

≤

< < <

.

= = =

.

.

for either uniaxial edgewise bending or biaxial bending for uniaxial flatwise bending or biaxial bending for biaxial bending


616.10 Design for Bearing 616.10.3 Bearing at an Angle with the Grain Hankinson’s Formula:

=

∗

∗

’ ’

where: = angle between direction of load and direction of grain (longitudinal axis of member), degrees

∗

′ 0

10

20

30

40

50

60

70

80

90

100


616.10 Design for Bearing 616.10.4 Bearing Area Factor, .

=

For some values of

:

Table 616.10-1 Bearing Length Factor,

13 (mm)

25

38

50

75

150 or 100 more

1.73 1.38 1.25 1.19 1.13 1.10 1.00

b

≤ 150 mm

75 mm

Section 617 SAWN LUMBER

617.1 617.2 617.3 617.4

General Reference Design Values Adjustment of Reference Design Values Special Design Considerations


617.1.3 Definitions (This has been restored) “Dimension” refers to lumber from 50 mm to 100 mm (nominal) thick, and 50 mm (nominal) or more in width. Dimension lumber is further classified as Structural Light Framing, Light Framing, Studs, and Joists and Planks. “Beams and Stringers” refers to lumber of rectangular cross section, 125 mm (nominal) or more thick, with width more than 50 mm greater than thickness, graded with respect to its strength in bending when loaded on the narrow face. “Posts and Timbers” refers to lumber of square or approximately square cross section, 125 mm x 125 mm (nominal) and larger, with width not more than 50 mm greater than thickness, graded primarily for use as posts or columns carrying longitudinal load. “Decking” refers to lumber from 50 mm to 100 mm (nominal) thick, tongued and grooved, or grooved for spline on the narrow face, and intended for use as a roof, floor, or wall membrane, Decking is graded for application in the flatwise direction, with the wide face of the decking in contact with the supporting members, as normally installed.


617.1.4 Moisture Service Condition of Lumber NEW Table 617.1-1(b) Wet Service Factor,

Table 617.1-1(a) Wet Service Factor,

Glued Laminated Timber (MC > 16%)

Visually Graded Sawn Lumber (MC > 19%)

Strength Property

Strength Property

and

and

All Dimension 0.851 Lumber Timbers Decking

1.00

2

1.00

0.97

0.67

0.80

1.00

1.00

0.67

0.91

0.852

0.67

1

When (

)(

) ≤ 8 MPa,

=1.0

2

When (

)(

) ≤ 5 MPa,

=1.0

0.90 1.00 0.90

Species

0.80 0.80 0.875 0.53

0.73

0.833

0.875


617.2.6 Compression Perpendicular to Grain, .

=

.

where .

= compression perpendicular to grain design value at 0.5 mm deformation limit, MPa = reference compression perpendicular to grain design value at 1 mm deformation limit (as tabulated in Tables 615.2-1 and 615.2-2), MPa


617.3 Adjustment of Reference Design Values Table 617.3-1 Applicability of Adjustment Factors for Sawn Lumber

r o t c a F n o i t a r u D d a o L

r o t c a F e c i v r e S t e W

r o t c a F e r u t a r e p m e T

r o t c a F y t i l i b a t S m a e B

′ ′

= =

x x

-

′

=

x

-

′

=

x

-

′

=

x

-

-

= =

x

-

x

-

′

r o t c a F e z i S

r o t c a F e s U t a l F

r o t c a F g n i s i c n I

r o t c a F e v i t i t e p e R

s y s t i e l i f n b r f i a t r t o o t t S S c c n F a g a n F i m l u k l o c u C B

r o t c a F a e r A g n i r a e B

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-


617.3.6 Size Factor 617.3.6.1 Where the depth of a rectangular sawn lumber bending member 125 mm or thicker exceeds 300 mm, the reference bending design values, , shall be multiplied by the following size factor: ⁄

=

where = size factor = depth of member, mm

617.3.6.2 For beams of circular cross section with a diameter greater than 340 mm, or for 300 mm or larger square beams loaded in the plane of the diagonal, the size factor shall be determined in accordance with 617.3.6.1 on the basis of an equivalent conventionally loaded square beam of the same cross-sectional area.

Section 617 SAWN LUMBER 617.3.7 Flat Use Factor, Bending design adjusted by size factors are based on loads applied to narrow face. When sawn lumber is used flatwise, (i.e. load applied to wide face) bending design value, , shall also be multiplied by the following flat-use factors: Table 617.3-2

Visually-Graded Sawn Lumber

Table 617.3-3 Machine-Graded1 Sawn Lumber

Flat-use Factors,

Flat-use Factors, Width (depth)

Thickness (breadth) 50mm &

100mm

75mm

Width

Thickness (breadth)

(depth)

50mm

50mm & 75mm

1.0

50 mm & 75 mm

1.0

-

100mm

1.1

100mm

1.1

1.0

125mm

1.1

125mm

1.1

1.05

150mm

1.15

150mm

1.15

1.05

200mm

1.15

200mm

1.15

1.05

250mm & wider

250mm & wider

1.20

1.1

1 Refer

to Section 622

1.20


617.3.8 Incising Factor, Many species readily accept preservative treatments, while others don’t. For species that are not easily treated, incising is used to make the treatment effective. Some design values for sawn lumber must be adjusted if incising is used to increase the penetration of the preservatives. The incising factors, , to be used shall be as follows: Table 617.3-4 Incising Factor, 0.95

0.80

0.80

0.80

1.0

For compression perpendicular to grain as well as for non-incised treated lumber, = . .


617.3.9 Repetitive Member Factor, A repetitive member system is defined as one that has:

1. Three or more parallel members of Dimension lumber or structural composite lumber; 2. Members spaced not more than 600 mm on center; 3. Members connected together by a load-distributing element such as roof, floor, or wall sheathing that has been designed or has been proven by experience to transmit the design load to adjacent members without displaying structural weakness or unacceptable deflection. For a repetitive member system, the reference may be multiplied by a repetitive member factor, = . . For all other framing systems, = . .


617.3.11 Buckling Stiffness Factor, Reference modulus of elasticity for beam and column stability, , shall be permitted to be multiplied by the buckling stiffness factor, , as specified in 617.4.2. (Can be used for wood trusses because of increased stiffness to axial loads) when ≤ 2.40 , shall be calculated as follows: where

when

=

+

ℓ

= effective column length of truss compression chord, mm = 0.62 for wood seasoned to 19% moisture content or less at the time of plywood attachment = 0.33 for unseasoned or partially seasoned wood at the time of plywood attachment = − . = 0.59 for visually graded lumber = 0.75 for machine evaluated lumber (MEL) = 0.82 for products with ≤ 0.11 > 2.40

,

shall be calculated based on

= 2.40


617.4 Special Design Considerations 617.4.1 Stability of Bending Members Alternative Design Consideration (a) / ≤ ; no lateral support shall be required. (b) < / ≤ ; the ends shall be held in position, as by full depth solid blocking, bridging, hangers, nailing, or bolting to other framing members, or other acceptable means. (c)

<

/ ≤ ; the compression edge of the member shall be held in line for its entire length to prevent lateral displacement, as by adequate sheathing or subflooring, and ends at point of bearing shall be held in position to prevent rotation and/or lateral displacement.


617.4 Special Design Considerations 617.4.1 Stability of Bending Members Alternative Design Consideration (d) < / ≤ ; bridging, full depth solid blocking or diagonal cross bracing shall be installed at intervals not exceeding 2.40 m, the compression edge of the member shall be held in line as by adequate sheathing or subflooring, and the ends at points of bearing shall be held in position to prevent rotation and/or lateral displacement. (e) < / ≤ ; both edges of the member shall be held in line for their entire length and ends at points of bearing shall be held in position to prevent rotation and/or lateral displacement. 617.4.1.3 If a bending member is subjected to both flexure and axial compression, the depth to breadth ratio shall be no more than 5 to 1 if one edge is firmly held in line. If under all combinations of load, the unbraced edge of the member is in tension, the depth to breadth ratio shall be no more than 6 to 1.


617.4.3 Notches Notches shall be permitted provided it satisfy the following limitations

Figure 617.4-1 Notch Limitations for Sawn Lumber Beams

Section 618 STRUCTURAL GLUED LAMINATED TIMBER

618.1 618.2 618.3 618.4

General Reference Design Values Adjustment of Reference Design Values Special Design Considerations


618.1.2 Definitions The term “structural glued laminated timber” refers to an engineered, stress rated product of a timber laminating plant, comprising assemblies of specially selected and prepared wood laminations bonded together with adhesives. The grain of all laminations is approximately parallel longitudinally. The separate laminations shall not exceed 50 mm in net thickness and are permitted to be comprised of: • one piece • pieces joined end-to-end to form any length • pieces placed or glued edge-to-edge to make wider ones • pieces bent to curved form during gluing.


618.2.2 Orientation of Member Reference design values for structural glued laminated timber are dependent on the orientation of the laminations relative to the applied loads. Subscripts are used to indicate design values corresponding to a given orientation. The orientations of the cross-sectional axes for structural glued laminated timber are shown in Figure 618.2-1. The x-x axis runs parallel to the wide face of the laminations. The y-y axis runs perpendicular to the wide face of the laminations.


618.2.4 Bending,

,

,

618.2.5 Compression Perpendicular to Grain, 618.2.6 Shear Parallel to Grain, 618.2.7 Modulus of Elasticity, 618.2.8 Radial Tension, 618.2.9 Radial Compression,

,

,

,

,

,


618.3 Adjustment of Reference Design Values Table 618.3-1 Applicability of Adjustment Factors for Structural Glued Laminated Timber 1 y n r t e e i o o l r i c t i t r i u c 1 t b v r r a r a r r o o a o a F t o r t u t e t t c c c D a S a e a S c p F a e F m m F d F t e m u a a l e e o W o T L B V

′ ′ ′ ′ ’

′

1

= = = = = = = =

The beam stability factor,

r o t c a F e s U t a l F

r o t c a F e r u t a v r u C

n n y t o o i i a i l t i t c c r r b r e a u r r A r o d o a t o o e t t e t t c R c S t c g n n c I F a r F a n F a i a r F s m s a l u a e e e r o B h t S C S

x

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

x

-

-

-

-

-

x

-

-

-

-

-

-

x

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

, shall not apply simultaneously with the volume factor,

, for structural glued laminated

timber bending members (see 618.3.6). Therefore, the lesser of these adjustment factors apply.


618.3.6 Volume Factor, When structural glued laminated timber members are loaded in bending about the x-x axis, the reference bending design values, , and , shall be multiplied by the following volume factor: where

=

.

≤

.

= length of bending member between points of zero moment, m = depth of bending member, mm = width (breadth) of bending member. For multiple piece width layups, b = width of widest piece used in the layup. Thus, b ≤ 275 mm. = 10 if specific value has not been established for the species used The volume factor, , shall not apply simultaneously with the beam stability factor, (see 616.3.3). Therefore, the lesser of these adjustment factors shall apply.


618.3.7 Flat Use Factor, When structural glued laminated timber is loaded in bending about the y-y axis and the member dimension parallel to the wide face of the laminations, (see Figure 618.3-1), is less than 300 mm, the reference bending design value, , shall be permitted to be multiplied by the flat use factor, , calculated by the following formula: ⁄

=

Figure 618.3-1 Depth,

, for Flat Use Factor


618.3.8 Curvature Factor, For curved portions of bending members, the reference bending design value shall be multiplied by the following curvature factor: =

−

where

= thickness of laminations, mm = radius of curvature of inside face of member, mm

=

for hardwoods

=

for softwoods

The curvature factor shall not apply to reference design values in the straight portion of a number, regardless of curvature elsewhere.


618.3.9 Stress Interaction Factor, For the tapered portion of bending members tapered on the compression face, the reference bending design value, , shall be multiplied by the following stress interaction factor: = +

+

tan

where

= angle of taper, degrees For members tapered on the compression face, the stress interaction factor, , shall not apply simultaneously with the volume factor, , therefore, the lesser of these adjustment factors shall apply.


618.3.9 Stress Interaction Factor, For the tapered portion of the bending members tapered on the tension face, the reference bending design value, , shall be multiplied by the following stress interaction factor: = where

+

+

tan

= angle of taper, degrees For members tapered on the tension face, the stress interaction factor, , shall not apply simultaneously with the beam stability factor, , therefore, the lesser of these adjustment factors shall apply. Taper cuts on the tension face of structural glued laminated timber beams are not recommended.


618.3.10 Shear Reduction Factor, The reference shear design values, and , shall be multiplied by the shear reduction factor, = 0.72 where any of the following conditions apply:  Design of non-prismatic members.  Design of members subject to impact or repetitive cyclic loading.  Design of members at notches (616.4.3.2).  Design of members at connections (616.4.3.3).


618.4 Special Design Considerations 618.4.1 Curved Bending Members with Constant Cross Section 618.4.1.3 The radial stress induced by a bending moment in a curved bending member of constant rectangular cross section is: =

where

= bending moment, N·m = radius of curvature at center line of member, mm Where the bending moment is in the direction tending to decrease curvature (increase the radius), the radial stress shall not exceed the adjusted radial tension design value perpendicular to the grain, ≤ ′, unless mechanical reinforcing sufficient to resist all radial stresses is used. In no case shall exceed (1/3) ′. Where the bending moment is in the direction tending to increase curvature (decrease the radius), the radial stress shall not exceed the adjusted radial compressional design ≤ ′.


618.4 Special Design Considerations 618.4.2 Double-Tapered Curved Bending Members 618.4.2.1 The bending stress induced by a bending moment, , at the peaked section of a double-tapered curved bending member (see Figure 618.4-1) shall be calculated as follows: = where

= empirical bending stress shape factor = + . = angle of roof slope, degrees = bending moment, N·m = depth at peaked section of member, mm The stress interaction factor from 618.3.9 shall apply for flexural design in the straight-tapered segments of double-tapered curved bending members.


618.4 Special Design Considerations 618.4.2 Double-Tapered Curved Bending Members 618.4.2.3 The radial stress induced by bending moment in a double-tapered curved member shall be calculated as follows: where

=

= empirical radial stress factor ⁄ + . tan . = . = empirical load-shape radial stress reduction factor ⁄ ⁄ + . − . + = . ≤ 0.3 for uniformly loaded members where ⁄ = . for members subject to constant moment = radius of curvature at center line of member, mm = + ⁄ = radius of curvature of inside face of member, mm

≤

.


618.4 Special Design Considerations 618.4.2.4 The deflection of double-tapered curved members shall be determined in accordance with 616.5, except that the mid-span deflection of a symmetrical double-tapered curved beam subject to uniform loads shall be permitted to be calculated by the following empirical formula: ∆ =

where

∆

= vertical deflection at midspan, mm + . + . − =

.

The horizontal deflection at the supports of symmetrical double-tapered curved beams shall be permitted to be estimated as ∆ =

where ∆

∆

= horizontal deflection at either support, mm ⁄ − ⁄ and = − = ⁄ +


618.4 Special Design Considerations 618.4.4 Tapered Straight Bending Members 618.4.4.3 The deflection of tapered straight beams shall be determined in accordance with 616.5, except that the maximum deflection of a tapered straight beam subject to uniform loads shall be permitted to be calculated as equivalent to the depth, , of an equivalent prismatic member of the same width where: = where

= depth at the small end of the member, mm = empirical constant derived from relationship of equations for deflection of tapered straight beams and prismatic beams.

Sections 619 to 622 SECTION 619 - TIMBER CONNECTORS AND FASTENERS The following tables are adopted from NDS 2015 Table 619.1-3 Split Ring Connector Reference Design Values Table 619.1-4 Shear Plate Connector Reference Design Values

SECTION 620 - CONVENTIONAL LIGHT-FRAME CONSTRUCTION DESIGN PROVISIONS SECTION 621 - METAL PLATE-CONNECTED WOOD TRUSS DESIGN SECTION 622 - USE OF MACHINE-GRADED LUMBER (MGL)

NOTE: Almost the same with NSCP 2010 



With minor corrections to conform with the NSCP 2015 updates Tables were re-arranged so as they appear right after the first time they were mentioned as practically as possible

Sample Problem No. 1 Simply Supported Beam Capacity Check Example (ASD)

A Mahogany, Big Leafed (80% Stress Grade) 4”x16” (88mm x 380mm actual size), 6meter simple span supports a hoist located at the center of the span. Taking into account the weight of the beam, determine the maximum allowable load on the hoist based on bending. Assume normal load duration. The beam is supported on a 2”x4” (50mm x 100mm) top plate. Lateral support is provided only at the ends of the member and the ends are considered pinned.

Sample Problem No. 1 Simply Supported Beam Capacity Check Example (ASD) A Mahogany, Big Leafed (80% Stress Grade) 4”x16” (88mm x 380mm actual size), 6-meter simple span supports a hoist located at the center of the span. Taking into account the weight of the beam, determine the maximum allowable load on the hoist based on bending. Assume normal load duration. The beam is supported on a 2”x4” (50mm x 100mm) top plate. Lateral support is provided only at the ends of the member and the ends are considered pinned. REFERENCE VALUES and Emin for Mahogany, Big leafed (80% Stress Grade) From Table 615.2.1 Reference Values for Visually Stress-Graded Unseasoned Timber … For bending . . . . . . . . F b = 16.5 MPa For comp. ║ grain . . . F c = 10.5 MPa For comp. ⊥ grain . . . F c⊥ = 3.83 MPa For shear ║ grain . . . F v = 2.71 MPa Elastic Modulus . . . . . E = 4,660 MPa Note: Value for Emin to be computed based on Table 617.3-1

COV E = 0.25 for V.G. sawn lumber E0.05 = E [ 1 – 1.645 COV E ] E0.05 = 4,660 [ 1 - 1.645(0.25)] E0.05 = 2,744 MPa Emin = E0.05 (1.03)/1.66 Emin = 2744 (1.03) /1.66 Emin = 1,703 MPa


ERRATA: Section 616.3.3.8 should read like this.

This part is missing but can also be found under Table 617.3-1

ASEP_ NSCP 2015 Chapter6 - WOOD.pdf

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